Update documentation of HDIO_DRIVE_RESET ioctl

Alter the entry for HDIO_DRIVE_RESET in Documentation/ioctl/hdio.txt to
reflect a functional change in the driver.  Besides, the entry has been
inaccurate before.

Signed-off-by: Elias Oltmanns <eo@nebensachen.de>
Cc: "Alan Cox" <alan@lxorguk.ukuu.org.uk>
Cc: "Randy Dunlap" <randy.dunlap@oracle.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>